Time system



N0V- 11, 1952 E. G. JOHNSON 2,617,245

TIME SYSTEM Filed Sept. 18, 1940 (lzxsoB-l) M6021) poles poles poles Imm||||||||||||nu|||||||||||||||||lmmumumuml||||||||||||||||||||m|||||||||||||||um||i|||||||||| F I G. 3 .f

F I G. 4

MMWR

Patented Nov. 11, 1952 UNITED STATES PATENT OFFICE TIME SYSTEM Ervin G. Johnson, akland,`Calif.

Application September 18, 1940, Serial-No-35731 SClaims.

1 This invention relates to time indication,` and particularly to time systems whereby the indications are remotely controlled.

It is one of the objects of this invention to provide a time system such that a minimum of mechanism in each time indicator is employed.

It is another object of the invention to provide a time system whereby the indications of the indicators are correct when the signal generator is correct.

It is a further object of this invention to provide a remote indicator capable of simultaneously indicating the positions of a plurality of members.

Other objects and advantages of the invention will become apparent upon consideration of the following speciication wherein reference is made to the accompanying drawing, in which:

Fig. l is an elevation, partially broken away, of an indicator such as employed in my invention;

.Fig 2 is a diagrammatic representation, including a sectional elevation through the indicator of Fig. 1, illustrating the remote time indicating system;

Fig. 3 is a plan view of a detail; and

Fig. 4 is a further view of the detail in Fig. 3.

The apparatus comprises a constant speed driving device such as a standard frequency electric motor of the synchronous type |00 which drives a combined indicator and screen |02 formed as a smooth disc fastened directly to the motor shaft |04 so as to provide but one integrated moving assembly for the clock proper. The disc |32 is provided with a plurality of radially related light permeable slits |05, |02, and lfll, which are preferably in radial alignment for convenience and simplicity in the clock marking. A multiple frequency light projector assembly ||2 is mounted in concentric relation to the shaft ieri and to dispose a plurality of individually isolated light projector elements |14, H5, H8, forming concentric rings adapted to register in radial disposition with the corresponding slits IQ, |58, and H0 at all times. Theprojection of the light from each projecting element is so directed that the light therefrom is restricted to the normal cylindrical path directed therefrom. The projector assembly ||2 is preferably enclosed by a window |20.

Each individual projector ring is illuminated by light'of a different frequency from the light frequency of any other ring. The lamps |22, which may bey one o1' more disposed around the ring so as to produce a cylinder of light at each energization of the lamp, are such 'as to be productive of visible'llight rays ,only at such times as the electrical voltage applied thereto is above a certain fixed minimum or. crest voltage. VThese lamps may, accordingly, be of the neon or glow type, or any typehaving a coordinate degree of discrimination for voltage of a minimum value, and having substantially instantaneous deenergization at such value. The lamps |24 and |25 in projectors IG and I8 are preferably of similar design to those in H4. The assembly |12 is desirably fastened directly to the stator frameoi motor |00.

The principle of 'this clock isperhaps made understandable at this point in the following manner: Consider the exterior surface of disc |02 as being black, and that, therefore, slit |06 will be emphasized only when light is projected therethrough from lamps |22. Assume also that motor |00 rotates at a speed of 3600 revolutions per minute, that is, revolutions per second. Assume that the second and minute scales are identical and as shown at the outer ring of Figure 8. Assume that lamps |22 illuminate only at the time that slit |051` lies at point 60, or 4at the time that slit 60 is in traverse of that second of arc at point 60. This condition can be attained by illuminating, or energizing lamps |22 at the times |00 is at 60 only. In this way the slit |06 is made toappear to stand still at the point 60, even though it has constant rotation and between energizations of lamps |22, has completely traversed'the 360 degrees of the clock face. Therefore, in order to make slit |06 appear to stand still, itis necessary to illuminate slit |05 fromsource ||4 lsixty times each second, and in order tomake the slit .appear to stand still at the point 60 the motor field and armature must be fixed in relation to each other in the .time sense, and they must be physically fixed with reference to the clock indicia as already described. Theassurnptions made aboveare simply to lay a foundation for an understanding of what actually produces an indication of time.

If slit |06 is illuminated 59 times per second, instead of 60 times per second, while the disc rotates 'at 60 revolutionsl per second asbeforeit isplain that the slit will move as far beyond the position of its last illumination in each interval of darkness, as the slit can move in .the time interval between it() Second and 1/;9'second. In one second the slit |01.:` will appear to travel inthe direction of rotation of the disc, 360 degrees, and appear to be. back whereit started from,.at the point 60. In similar manner, `byincreasing the frequency of illumination, to 61 cycles ,per

second, the successive illuminations occur at shorter arcuate intervals of rotations of the screen, and the slit appears to rotate counter the disc rotation. In this way the second is split up by illuminating the slit 59 or 6l times during its apparent travel through 360 degrees of arc.

Inasmuch as normal clocks indicate larger units of time, as seconds, minutes, hours and half days, it is preferable to illuminate the various slits E96, 108, and H by such frequencies as produce apparent rotations of the slits, once per minute, once per hour, and once each twelve hours. It has been shown that this apparent rotation in any unit of time can be produced by differing the number of illuminations of the slit by one from the number of traverses of the slit of any particular point in unit of time sought to be indicated.

For indicating seconds, therefore, there being sixty seconds in the minute, since the slit H36 traverses the point 60 3600 times in sixty seconds, and illumination of the slit either 3599 times per minute, or 3601 times per minute, causes the slit to appear to travel through 360 degrees each minute. In each second it appears to travel 6 geometrical degrees. Accordingly, for a conventional clock having a second indicator, the lamps E22 may be illuminated 3599, or 3601 times per minute, on the average, in order to indicate seconds, and depending upon the desired direction of apparent rotation.

By calculation, the lamps lZd are determined to require a frequency of energization such that they project light a num'ber of times differing by one from the number of traverses of the slit past the point 60 during one hour, which, with the disc speed here selected is 60 60 60 plus or minus 1 as before each hour; `and by similar token, the slit HG must be illuminated 60 60 60 12 plus or minus one times per half day, the plus or minus supplying the direction of apparent rotation. All of these frequencies lie within the range from 59 to 61 cycles per second. However, these frequencies can be halved or quartered, and a similar effect at half or quarter of the number of illuminations of the traverses secured.

The different frequencies of illumination of the lamps may best be supplied from frequency generators such as high fidelity vacuum tube oscillators, or by a synchronized system such as shown in Figure 2, wherein it is indicated that the shaft mit may be extended to drive a set of gears which successively step down their rotational rates. For example, shaft 128 rotates once per second and carries 59 poles designed to generate a voltage of 59 cycles per second, the crests of which always occur at the time of transit of |06 past the point 60, if it is desired to indicate fractions of seconds. In the conventional clock system, lamps E22 are illuminated so as to indicate seconds, under control of the generator driven by shaft 39, which rotates once per minute and carries 3599 or 3601 poles to generate a corresponding frequency. In like manner shafts |32 and 134 rotate once per hour and once per half day respectively and have the required number of poles to generate the required frequency. The synchronism may be effected by direct connection of |94 to |28, or any well known system of synchronizing by remote control may be employed.

Since the apparent relative positions of the slits is only one depending upon the source of energy, the slits will appear to be in a radial line, only at noon and midnight, if the frequencies are properly related in time at their sources. For this reason, it is desirable to make the clock indicia rotate for adjustment so that the clock may be set on the hour, on the 12 hour, or on the minute, without other than a general knowledge as to the hour of the day from any other source. At coincidence of the slits, which occurs only at midday or midnight, it makes no difference. The fact of coincidence alone indicates 12 oclock, and the dial can be positioned in alignment at this time. In fact, with some practice, the clock can be set without outside knowledge of the time, by bearing in mind that (l) the hour indicator slit Il@ should be apparently coincident with an hour indicia when the minute slit 168 and the second slit are both at the 60 indicia, -or (2) the hour indicator should be exactly half way between two hour indicia when the minute slit is at the indicia 30 and the second slit is at the indicia 60. The hour or half hour which Iconforms to these conditions can easily be identified.

Because of this peculiarity, time can be directly indicated from a radio broadcasting station on the face of the clock, the frequencies being broadcast from a central control and operating to control, by radio frequency, the local circuit which illuminates the lamps 122 etc. This method of transmitting time signals is particularly effective for navigation.

For example, a conventional radio receiver circuit, designed to accept radio frequency signals with the superimposed time frequencies above described, operates to segregate the three time signals by means of suitable filters capable only of passing the particular frequency of a lamp frequency f3 for example, feed that energy to a power ampliiier, and thence deliver the energy necessary to illuminate the slits.

By employing the screen, of course, and illumination over the entire ring, there is always a point of registry between source of illumination and the slits.

If the oscillation generators 28, |30, H32, 134, or f1, f2, etc. are locked in correct relation, whether by an electrical tie or by direct mechanical interlock, whether by selsyn motors or by the same shaft its, the clocks so tied in to the same system are automatically, `and without the need of occasional resetting signals, kept in correct time. inasmuch as only one rotating part is used in the clock proper, and inasmuch as only one set of frequency generators is necessary to control all clocks in a system, it is obvious that mechanical difculties are relatively small. Furthermore, even though one or more lamps may go bad, or even though one source of frequency goes out of operation, the fact does not prevent some time indication, and moreover, the clock gives denite evidence that the time is not properly indicated, because it does not indicate if any part of the time unit indicating elements are not functioning.

I claim:

l. In. combination, a rotatable member, means for rotating said member with periodic motion, marks on said member, means individual to said marks for rendering said marks visible as such only periodically during rotation; the period of the periodic motion and the durations of the visibilities of the marks being in such ratios that the marks are visible during small fractional parts of the period of the periodic motion though they may appear as continuously visible; and the period of the periodic motion and the periods of the visibility rendering means being such that the marks appear to make complete rotations in periods of time which are integral multiples of the period of said member; and the periods of apparent rotations of the marks bear Whole-number ratios to each other.

2. In a time indicating system: an alternating current time signal generator including a driving member and a driven generator; a time indicating assembly comprising a synchronous motor, a rotary member driven by said motor having a time indicating mark thereon, time indicia adjacent the path of movement of the mark, and illuminating means adjacent the path of movement of the mark for illuminating the same when energized; means for causing the driving member of the time signal generator and the synchronous motor of the indicating assembly to run in locked relationship; means for transmitting the signals from the generator to the illuminating means for periodically illuminating the mark; said time signal generator including means for generating an alternating current having a period such that the mark appears to move from one indicia to another in the length of time denoted by the difference in value of such indicia.

3. In combination, a synchronous motor, a disk driven thereby, a mark on said disk, time indicia adjacent the path of movement of the mark, a lrst source of alternating current for driving said motor, and an alternating current illuminating system for illuminating said mark periodically While the mark is in motion, means for xing the period of the alternating current of the illuminating system at a constant value different from that of the rst source Which constant value causes the mark to appear to rotate exactly once in a standard period of time While the disc rotates a Whole number of times during such standard period of time.

4. In combination, a synchronous motor, a rotatable member driven thereby at a constant speed of rotation, means providing a time scale adjacent said rotatable member, said rotatable member having a series of light passing slits therethrough positioned on said member so that they rotate in separate paths, a rst lighting means disposed adjacent the path of movement of one of said slits including means for projecting the light therefrom through said one slit only in any of its positions in movement; a second lighting means disposed adjacent another of the slits including means for projecting light therefrom through said other slit only in any of its positions in movement; and separate means for energizing the lighting means associated with each slit in such manner that the slits appear to travel in the direction of the time scale in proportion to time and in such manner that one slit appears to travel at a rate which is a simple multiple or divisor of the apparent rate of travel of any other of the slits and in conjunction therewith to indicate time.

5. A construction according to claim 4, said lighting energizing means being driven by the synchronous motor shaft.

6. A construction according to claim 4, said lighting energizing means including xed frequency oscillators.

7. A construction according to claim 4, and means tying the motor and the lighting energizing means in synchronized relation.

8. In combination, a synchronous motor, a first source of alternating current of a certain frequency for energizing said motor; means driven by said synchronous motor for producing a second alternating current of a frequency differing by one cycle per unit of time from the said certain frequency, a time indicating mark driven by said motor, a time scale adjacent the path of the mark, and illuminating means energized periodically by the second alternating current arranged to render the mark visible in a manner to indicate time.

ERVIN G. JOHNSON.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,766,074 Hiers June 24, 1930 1,940,411 Trischknecht Dec. 19, 1933 2,055,982 Nicolson Sept. 20, 1936 2,063,032 Factor Dec. 8, 1936 2,066,349 Hellweg et al Jan. 5, 1937 2,088,478 Kovalsky July 27, 1937 2,092,039 Young Sept. 7, 1937 2,133,581 Simmon Oct. 18, 1938 2,231,849 Gibbs et al Feb. 11, 1941 2,268,133 Carlson Dec. 30, 1941 2,272,781 Stone et al Feb. 10, 1942 FOREIGN PATENTS Number Country Date 532,929 Germany Sept. 5, 1930 

